Re: [PATCHv9 0/9] Xen: extend kexec hypercall for use with pv-ops kernels

[David Vrabel <dvrabel@cantab.net>]

On 18/10/2013 19:40, Daniel Kiper wrote:
> On Tue, Oct 08, 2013 at 05:55:01PM +0100, David Vrabel wrote:
>> The series (for Xen 4.4) improves the kexec hypercall by making Xen
>> responsible for loading and relocating the image.  This allows kexec
>> to be usable by pv-ops kernels and should allow kexec to be usable
>> from a HVM or PVH privileged domain.
> 
> I could not load panic image because Xen crashes in following way:
> 
> (XEN) ----[ Xen-4.4-unstable  x86_64  debug=y  Tainted:    C ]----
[...]
> (XEN) Xen call trace:
> (XEN)    [<ffff82d080114ef2>] kimage_free+0x67/0xd2
> (XEN)    [<ffff82d0801151f9>] do_kimage_alloc+0x29c/0x2f0
> (XEN)    [<ffff82d0801152fe>] kimage_alloc+0xb1/0xe6
> (XEN)    [<ffff82d0801144c0>] do_kexec_op_internal+0x68e/0x789
> (XEN)    [<ffff82d0801145c9>] do_kexec_op+0xe/0x12
> (XEN)    [<ffff82d0802268cb>] syscall_enter+0xeb/0x145

The appended patch should fix this crash which only occurs if there's an
error in do_kimage_alloc().

> Normal kernel could be loaded but when it is executed something
> crashes very early. Following message is displayed

Both normal and panic images work fine for me.  You're going to have to
provide more details.

David

8<---------------------------------
--- a/xen/common/kimage.c
+++ b/xen/common/kimage.c
@@ -179,7 +179,7 @@ static int do_kimage_alloc(struct kexec_image
**rimage, paddr_t entry,

page_to_maddr(image->control_code_page),

page_to_maddr(image->control_code_page));
     if ( result < 0 )
-        return result;
+        goto out;

     /* Add an empty indirection page. */
     image->entry_page = kimage_alloc_control_page(image, 0);
@@ -188,7 +188,7 @@ static int do_kimage_alloc(struct kexec_image
**rimage, paddr_t entry,
     result = machine_kexec_add_page(image,
page_to_maddr(image->entry_page),
                                     page_to_maddr(image->entry_page));
     if ( result < 0 )
-        return result;
+        goto out;

     image->head = page_to_maddr(image->entry_page);

@@ -510,15 +510,14 @@ static void kimage_free_entry(kimage_entry_t entry)
     free_domheap_page(page);
 }

-void kimage_free(struct kexec_image *image)
+static void kimage_free_all_entries(struct kexec_image *image)
 {
     kimage_entry_t *ptr, entry;
     kimage_entry_t ind = 0;

-    if ( !image )
+    if ( !image->head )
         return;

-    kimage_free_extra_pages(image);
     for_each_kimage_entry(image, ptr, entry)
     {
         if ( entry & IND_INDIRECTION )
@@ -537,8 +536,15 @@ void kimage_free(struct kexec_image *image)
     /* Free the final indirection page. */
     if ( ind & IND_INDIRECTION )
         kimage_free_entry(ind);
+}

-    /* Free the kexec control pages. */
+void kimage_free(struct kexec_image *image)
+{
+    if ( !image )
+        return;
+
+    kimage_free_extra_pages(image);
+    kimage_free_all_entries(image);
     kimage_free_page_list(&image->control_pages);
     xfree(image->segments);
     xfree(image);